Piezoelectric resonator with scattering-prevention film to prevent short-circuit of the excitation electrode

ABSTRACT

To provide a piezoelectric resonator in which a casing houses a tuning-fork piezoelectric resonator element and whose failure occurrence caused when shavings of adjustment films scatter and adhere to excitation electrodes is prevented. In a method of manufacturing a quartz-crystal resonator in which a casing  20  houses a quartz-crystal resonator element  10  including a tuning-fork quartz-crystal piece  11 , excitation electrodes  6   a   , 6   b   , 6   c , and adjustment films  8  for frequency adjustment, a wall surface  29  preventing shavings of the adjustment films  8  from scattering is formed between an atmosphere where the excitation electrodes  6   a   , 6   b   , 6   c  are located and an atmosphere where the adjustment films  8  are located inside the casing  20 , and when the adjustment films  8  are shaved by a laser beam in order to adjust the frequency of the quartz-crystal resonator element  10 , the wall surface  29  prevents the scattering shavings from adhering to the excitation electrodes  6   a   , 6   b   , 6   c  and causing a short circuit thereof, thereby reducing the occurrence of a failure.

This is a Divisional Application of Ser. No. 12/590,108 filed Nov. 3,2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric resonator in which atuning-fork piezoelectric resonator element made of, for example, quartzcrystal or the like is housed in a casing, and to a manufacturingtechnique thereof.

2. Description of the Related Art

Conventional piezoelectric resonators include a tuning-forkquartz-crystal resonator adopted as a signal source or the like whichkeeps pace of a watch. Being small in size, low in cost, and low inpower consumption, the tuning-fork quartz-crystal resonator is veryeffective as a piezoelectric resonator mounted in a small electronicdevice such as a watch and is coming into use in wider applications.FIG. 9( a) to FIG. 9( c) show an example of this conventionaltuning-fork quartz-crystal resonator. The tuning-fork quartz-crystalresonator is structured such that a tuning-fork quartz-crystal resonatorelement 100 shown in FIG. 9( a) is mounted in a casing 120 shown in FIG.9( b) via a conductive adhesive 122.

The quartz-crystal resonator element 100 has a base portion 101 and two(pair of) oscillating arms 102 which are set parallel with each other ata predetermined interval and extend in one direction from the baseportion 101. In the drawings, 105 a and 105 b denote groove portionsformed in one surface and a rear surface of each of the oscillating arms102 to enhance oscillation efficiency and reduce a power loss, 106denotes excitation electrodes exciting tuning-fork oscillation based onbending oscillation in the groove portions 105 a, 105 b and peripheralareas thereof, 107 denotes lead electrodes, and 120 a denotes a covermounted on the casing 120 to seal it.

In such a quartz-crystal resonator, adjustment films 108 are formed forfrequency adjustment on tips of the oscillating arms 102. The adjustmentfilms 108 are formed so as to be apart from the excitation electrodes106, and as shown in FIG. 9( c), are shaved for the adjustment ofthickness and area thereof by, for example, laser irradiation by a laserirradiator 30. However, when the adjustment films 108 are shaved,shavings of the adjustment films 108 scatter and adhere to theexcitation electrodes 106 to cause a short-circuit of the excitationelectrodes 106, which involves a risk that the quartz-crystal resonatormay become a defective product.

To solve this problem, there has been conventionally proposed thefollowing methods. For example, patent document 1 describes aquartz-crystal resonator element in which an excitation electrode and anadjustment film are provided on a tuning-fork quartz-crystal piece and ahigh-melting point scattering prevention film is formed so as to coverthe excitation electrode and the adjustment film. In this quartz-crystalresonator, the adjustment film is melted by laser to be shaved, and thescattering prevention film prevents the adjustment film from scatteringat the time of the frequency adjustment. Further, the adjustment films,even if scattering toward the excitation electrode side, adheres ontothe scattering prevention film, which can prevent the short-circuit ofthe excitation electrode. Then, shavings of the cut adjustment film aredischarged from a hole that the laser forms in the scattering preventionfilm. However, forming the scattering prevention film in thequartz-crystal resonator element increases the number of elementmanufacturing processes and makes the element one size larger, leadingto a size increase of the quartz-crystal resonator itself.

Further, patent document 2 describes a quartz-crystal resonator inwhich, in order to prevent a quartz-crystal resonator element fromchipping due to the collision of its oscillating ends with a wallportion of a casing, projecting portions are provided on an uppersurface and a lower surface of the casing so that an upper surface and alower surface of the quartz-crystal resonator element except its tipportion come into contact with the projecting portions. Thequartz-crystal resonator of the patent document 2 can prevent chippingof a quartz-crystal piece which becomes the element, but gives nodescription regarding the prevention of the adhesion of shavings ofadjustment films. Therefore, the quartz-crystal resonator of the patentdocument 2 also involves a risk of becoming a defective product due tothe aforesaid problem.

-   [Patent Document 1] Japanese Patent Application Laid-open No.    2000-223998 (paragraph No. 0019, 0020)-   [Patent Document 2] Japanese Patent Application Laid-open No.    2003-133883 (paragraph No. 0011)

SUMMARY OF THE INVENTION

The present invention was made under such circumstances and has anobject to provide a piezoelectric resonator in which a tuning-forkpiezoelectric resonator element is provided in a casing, and whosefailure caused when shavings of adjustment films scatter and adhere toexcitation electrodes can be prevented, and to provide an electroniccomponent including the piezoelectric resonator and a method ofmanufacturing the piezoelectric resonator.

The present invention is a method of manufacturing a piezoelectricresonator in which a casing houses a piezoelectric resonator element,the method including:

manufacturing the piezoelectric resonator element including: atuning-fork piezoelectric oscillating piece from whose base portion twooscillating arms extend in parallel with each other; excitationelectrodes formed on the oscillating arms; adjustment films forfrequency adjustment formed on tip sides of the oscillating arms so asto be apart from the excitation electrodes; and a lead electrode formedon the base portion;

forming the casing including a wall surface which is provided between anatmosphere where the excitation electrodes are located and an atmospherewhere the adjustment films are located and prevents shavings fromscattering to the atmosphere where the excitation electrodes are locatedwhen the adjustment films are shaved,

mounting the piezoelectric resonator element in the casing; and

shaving the adjustment films by a laser beam to adjust a frequency ofthe piezoelectric resonator element in the casing.

The wall surface is, for example, a surface on an adjustment film sideof a wall portion projecting from an inner wall surface of the casing.Further, in the method of manufacturing the piezoelectric resonator ofthe present invention, for example, a portion, of the casing, facing atleast one of one surface side and another surface side of an adjustmentfilm formation area of the piezoelectric oscillating piece is made of alight transmitting material and the casing has a discharge port fordischarging the shavings on a side facing the atmosphere where theadjustment films are located

The present invention is a piezoelectric resonator including:

a casing;

a piezoelectric resonator element housed in the casing and including: atuning-fork piezoelectric oscillating piece from whose base portion twooscillating arms extend in parallel with each other; excitationelectrodes formed on the oscillating arms; adjustment films forfrequency adjustment formed on tip sides of the oscillating arms so asto be apart from the excitation electrodes; and a lead electrode formedon the base portion; and

a wall surface provided in the casing, located between an atmospherewhere the excitation electrodes are located and an atmosphere where theadjustment films are located, and preventing shavings from scattering tothe atmosphere where the excitation electrodes are located when theadjustment films are shaved.

Further, in the piezoelectric resonator of the present invention, thewall surface may be, for example, a surface on an adjustment film sideof a wall portion projecting from an inner wall surface of the casing.Further, in the piezoelectric resonator of the present invention, aportion, of the casing, facing at least one of one surface side andanother surface side of an adjustment film formation area of thepiezoelectric oscillating piece may be made of a light transmittingmaterial and the casing may have a discharge port for discharging theshavings on a side facing the atmosphere where the adjustment films arelocated An electronic component of the present invention includes: anyof the above-described piezoelectric resonators; a substrate on whichthe piezoelectric resonator is mounted; and an oscillator circuitoscillating the piezoelectric resonator.

According to the present invention, inside the casing of thepiezoelectric resonator, the wall portion is interposed between theatmosphere where the excitation electrodes are located and theatmosphere where the adjustment films are located, and therefore, whenthe adjustment films are shaved for frequency adjustment, the wallportion blocks off the scattering shavings to reduce the adhesion of theshavings to the excitation electrodes. This prevents the occurrence of afailure of the piezoelectric resonator due to a short-circuit or thelike of the excitation electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) and FIG. 1( b) are explanatory views illustrating thestructure of a quartz-crystal resonator of an embodiment;

FIG. 2 is a perspective view of a quartz-crystal resonator element ofthis embodiment;

FIG. 3( a) to FIG. 3( c) are first explanatory views illustratingmanufacturing processes of the quartz-crystal resonator of thisembodiment;

FIG. 4( a) to FIG. 4( c) are second explanatory views illustrating themanufacturing processes of the quartz-crystal resonator of thisembodiment;

FIG. 5( a) to FIG. 5( c) are explanatory views illustrating frequencyadjustment of the quartz-crystal resonator of this embodiment;

FIG. 6( a) to FIG. 6( c) are explanatory views illustrating thestructure of a quartz-crystal resonator of another embodiment;

FIG. 7( a) to FIG. 7( d) are explanatory views illustrating frequencyadjustment of the quartz-crystal resonator of the other embodiment;

FIG. 8( a) and FIG. 8( b) are explanatory views illustrating thestructure of a quartz-crystal resonator of still another embodiment; and

FIG. 9( a) to FIG. 9( c) are explanatory views illustrating aconventional tuning-fork quartz-crystal resonator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment in which the piezoelectric resonator of the presentinvention is applied to a quartz-crystal resonator will be describedwith reference to FIG. 1( a) to FIG. 5( c). As shown in FIG. 1( a) andFIG. 1( b), the quartz-crystal resonator is structured such that aquartz-crystal resonator element 10 is mounted in a casing 20. As shownin FIG. 2, the quartz-crystal resonator element 10 is formed such thatgroove portions 5 a, 5 b, excitation electrodes 6 a, 6 b, 6 c, leadelectrodes 7, and adjustment films 8 as weights for frequency adjustmentare provided on a quartz-crystal piece 11 in a tuning fork shape whichcorresponds to a piezoelectric oscillating piece of the presentinvention and which includes a base portion 1 in a substantiallyrectangular shape and two oscillating arms 2 extending from the baseportion 1 in parallel with each other. Note that in FIG. 2, formationareas of the excitation electrodes 6 a, 6 b, 6 c, the lead electrodes 7,the adjustment films 8, and so on are hatched for easier understandingof the positions thereof.

The groove portions 5 a, 5 b are arranged in line in a longitudinaldirection in each of the oscillating arms 2 and are each formed in arectangular shape. The excitation electrodes 6 a, 6 b are provided oninner peripheral surfaces of the groove portions 5 a, 5 b, and theexcitation electrodes 6 c are provided in peripheral areas of the grooveportions 5 a, 5 b so as to be a predetermined interval apart from thegroove portions 5 a, 5 b. The excitation electrodes 6 a, 6 b, 6 c areconnected to the lead electrodes 7 formed on the base portion 1.Further, the adjustment films 8 are provided on tip sides of theoscillating arms 2 so as to be apart from the excitation electrodes 6 c.The adjustment films 8 are made of, for example, metal films made of Cr(chromium) and Au (gold).

As shown in FIG. 1( a) and FIG. 3( a), the casing 20 is made of, forexample, borosilicate glass capable of transmitting a laser beam and isformed in a rectangular parallelepiped shape with its upper surface sideopen, and an outer wall 20 b is provided along a peripheral edgethereof. On an upper surface of the outer wall 20 b, that is, itssurface bonded to a cover 20 a (to be described later), a metal film 3made of, for example, aluminum or the like, is formed for use foranodic-bonding of the casing 20 and the cover 20 a. Further, the casing20 has a discharge port 24 and a lower wall portion 25. The dischargeport 24 is an opening with a 150 μm diameter, for instance, which isformed in a projection area of the adjustment films 8 in a bottomportion of the casing 20 and through which shavings of the adjustmentfilms 8 are discharged to the outside.

The lower wall portion 25 is formed to extend from the bottom portion ofthe casing 20 toward the casing upper surface, and when thequartz-crystal resonator element 10 is mounted, the lower wall portion25 is orthogonal to the quartz-crystal resonator element 10, that is,vertical to the quartz-crystal resonator element 10 set horizontal sothat an atmosphere between the quartz-crystal resonator element 10 andthe bottom surface of the casing 20 is divided into an atmosphere wherethe excitation electrodes 6 c are located and an atmosphere where theadjustment films 8 are located. The lower wall portion 25 is formed sothat its edge portion does not come into contact with the oscillatingarms 2 which are oscillating.

Further, the casing 20 has, in its longitudinal one side portion,totally two mounting electrodes 21, one for each of left and rightportions of the casing 20. The mounting electrodes 21 are provided onupper surfaces of mounting portions 21 a provided on the bottom portionof the casing 20 and each made of an insulator, and are electricallyconnected to external electrodes 23 which are provided on the bottomportion of the casing 20, via electrodes (not shown) provided inside themounting portions 21 a. Note that in FIG. 1( b) and FIGS. 3( a) to 3(c),cross sections taken along the arrow A-A in FIG. 1( a) are shown and theillustration of the quartz-crystal resonator element 10 is simplifiedfor convenience of description.

On the upper surface side of the casing 20, the cover 20 a for sealingthe casing 20 is attached. Similarly to the casing 20, the cover 20 a ismade of, for example, borosilicate glass capable of transmitting a laserbeam. Further, the cover 20 a has an upper wall portion 26. As shown inFIG. 1( b) and FIG. 3( a), the upper wall portion 26 is formed to extendfrom the cover 20 a toward the casing lower surface, and when thequartz-crystal resonator element 10 is mounted, the upper wall portion26 is orthogonal to the quartz-crystal resonator element 10, that is,vertical to the quartz-crystal resonator element 10 set horizontal sothat an atmosphere between the quartz-crystal resonator element 10 andthe cover 20 a is divided into an atmosphere where the excitationelectrodes 6 c are located and an atmosphere where the adjustment films8 are located

Further, the upper wall portion 26 is formed so that its edge portiondoes not come into contact with the oscillating arms 2 which areoscillating. When the quartz-crystal resonator is assembled, the lowerwall portion 25 and the upper wall portion 26 form, inside the casing20, one wall portion 27 having a passage area 28 formed in a shapeallowing the passage of the oscillating arms 2 and not hindering theoscillation of the oscillating arms 2. In this embodiment, a wallsurface 29, of the wall portion 27, facing the atmosphere where theadjustment films 8 are located corresponds to a wall surface of thepresent invention (see FIG. 4( c) to be described later).

Next, methods of manufacturing the quartz-crystal resonator element 10,the casing 20, and the cover 20 a will be briefly described. First, themethod of manufacturing the quartz-crystal resonator element 10 will bedescribed. A metal film and a resist pattern are stacked on aquartz-crystal wafer W being a piezoelectric substrate and a largenumber of the quartz-crystal pieces 11 in a tuning fork shape includingthe grooves are formed by using wet etching. Thereafter, the excitationelectrodes 6 a, 6 b, 6 c, the lead electrodes 7, and the adjustmentfilms 8 are formed on the quartz-crystal pieces 11 by patterning, andthe wafer W is cut by dicing into the individual quartz-crystalresonator elements 10.

The casing 20 and the cover 20 a are each formed by etching followingthe formation of an etching mask on a glass substrate. In the casing 20,first, the outer wall 20 b is formed in a state where glass in aformation area of the lower wall portion 25 is left, and thereafter, byetching following the formation of an etching mask corresponding to thedischarge port 24 and the lower wall portion 25, the discharge port 24and the lower wall portion 25 are formed. Then, the aforesaid metal film3 is formed on the upper portion of the outer wall 20 b. Further, in thecover 20 a, by etching following the formation of an etching maskcorresponding to the upper wall portion 26, the upper wall portion 26 isformed. Incidentally, in this embodiment, the casing 20 and the cover 20a are made of borosilicate glass, but as an embodiment of the presentinvention, the material of the casing may be any substance capable oftransmitting a laser beam, and may be, for example, soda glass or quartzcrystal. Further, when the casing and the cover are made of quartzcrystal, the quartz-crystal resonator may be formed in such a mannerthat the casing and the cover are formed by using quartz-crystalsubstrates and the quartz-crystal substrates and a quartz-crystalsubstrate on which the quartz-crystal resonator element is formed arestacked.

Next, a method of manufacturing the quartz-crystal resonator will bedescribed with reference to FIGS. 3( a) to 3(c) and FIGS. 4( a) to 4(c).As shown in FIG. 3( b), FIG. 4( a), and FIG. 4( b), the lead electrodes7 and the mounting electrodes 21 are electrically connected viaconductive adhesives 22, so that the individually cut quartz-crystalresonator element 10 is mounted in the casing 20 to be parallel with thebottom surface of the casing 20, next the cover 20 a seals the uppersurface side of the casing 20 as shown in FIG. 3( c) and FIG. 4( c), anda DC current is applied for a predetermined time to the metal film 3formed on the upper surface of the outer wall 20 b, whereby the cover 20a and the casing 20 are anodic-bonded.

After the quartz-crystal resonator including the quartz-crystalresonator element 10 is formed by the above-described processes, thequartz-crystal resonator is next mounted on a jig for frequencyadjustment (not shown) and inserted into a vacuum chamber (not shown),the quartz-crystal resonator element 10 is oscillated in a vacuumatmosphere, and while its frequency is measured, the adjustment films 8are shaved by a laser cutter 30 until the frequency becomes a desiredvalue. The adjustment films 8 are composed of, for example, blocks witha predetermined size arranged in an island form, and for the frequencyadjustment, blocks in number corresponding to a difference between themeasured frequency and a set frequency are removed. For this blockremoval work, according to the difference between the measured frequencyand the set frequency, a control unit outputs a control signal to amoving mechanism relatively moving the laser cutter 30 and the jig on aplane, and according to the control signal, the blocks to be removed ofthe adjustment films 8 are sequentially irradiated with the laser beam.

In the process of shaving the adjustment films 8, it is possible notonly to shave the adjustment films 8 only on front surfaces 2 a or rearsurfaces 2 b of the oscillating arms 2 but also to shave the adjustmentfilms 8 on both of the front surfaces 2 a and the rear surfaces 2 b ofthe oscillating arms 2 at one time, and either one is selected in thework. When the adjustment films 8 only on one side, for example, theadjustment films 8 only on the front surfaces 2 a of the oscillatingarms 2 are shaved, a module generating the laser beam of the lasercutter 30 is changed to a module generating a short-wavelength laserbeam and a depth of focus of the laser beam is finely adjusted so thatonly the adjustment films 8 on the front surfaces 2 a of the oscillatingarms 2 can be shaved as shown in FIG. 5( a). Then, the laser beam isfocused on positions, of the front surfaces 2 a, where the adjustmentfilms 8 are formed. Consequently, the laser beam can be irradiated sothat it passes through the cover 20 a to shave the adjustment films 8 onthe front surfaces 2 a. At this time, by adjusting the depth of focus ofthe laser beam so that heat of the laser beam is not transferred to theadjustment films 8 on the rear surfaces 2 b, it is possible to preventthe laser beam from passing through the oscillating arms 2 and shavingthe adjustment films 8 on the rear surfaces 2 b, and consequently, onlythe adjustment films 8 on the front surfaces 2 a can be shaved.

On the other hand, when the adjustment films 8 on both of the frontsurfaces 2 a and the rear surfaces 2 b of the oscillating arms 2 areshaved, by adjusting the depth of focus of the laser beam so that theheat of the laser beam is transferred to the adjustment films 8 on therear surfaces 2 b, the laser beam is made to pass through theoscillating arms 2 to shave the adjustment films 8 on the rear surface 2b, or by changing the module generating the laser beam to a modulegenerating a long-wavelength laser beam, the laser beam of the lasercutter 30 is focused on the positions, of, for example, the frontsurfaces 2 a or the rear surfaces 2 b, where the adjustment films 8 areformed. Consequently, the laser beam is irradiated so that it passesthrough the cover 20 a to shave the adjustment films 8 on the frontsurfaces 2 a, and further passes through the oscillating arms 2 to shavethe adjustment films 8 on the rear surfaces 2 b, and consequently, theadjustment films 8 on the front surfaces 2 a and the rear surfaces 2 bcan be shaved at one time. Incidentally, when only the adjustment films8 on the rear surfaces 2 b are shaved, the quartz-crystal resonator isturned upside down and the adjustment films 8 on the rear surfaces 2 bare directly irradiated with the laser beam.

As shown in FIGS. 5( a), 5(b), during the process of shaving theadjustment films 8, part of the adjustment films 8 evaporate and partthereof scatter from the front surfaces 2 a and the rear surfaces 2 b ina solid form or while left in a liquid form. Owing to the presence ofthe wall surface 29, shavings scattering toward the atmosphere where theexcitation electrodes 6 a, 6 b, 6 c are located, out of the scatteringshavings, collide with the wall surface 29 to drop toward the atmospherewhere the adjustment films 8 are located and the shavings of theadjustment films 8 accumulate in the atmosphere where the adjustmentfilms 8 are located, inside the casing 20.

The evaporating adjustment films 8 and the shavings are discharged outof the casing 20 through the discharge port 24. Since the process ofshaving the adjustment films 8 is performed in a vacuum chamber, theatmosphere in the casing 20 is constantly sucked by a vacuum pump (notshown) in the vacuum chamber via the discharge port 24. The evaporatingadjustment films 8 and the shavings are discharged to the outsidethrough the discharge port 24 by a suction force of the vacuum pump.Consequently, it is possible to lower the probability that thequartz-crystal resonator becomes defective due to the adhesion of theshavings to the quartz-crystal resonator after the frequency adjustment.Through the above-described processes, the quartz-crystal resonator witha desired frequency is manufactured, and after the discharge port 24 isthereafter sealed, the quartz-crystal resonator is mounted on anelectronic component such as a watch.

According to the embodiment described above, in the casing 20 of thequartz-crystal resonator, the wall surface 29 is interposed between theatmosphere where the excitation electrodes 6 a, 6 b, 6 c are located andthe atmosphere where the adjustment films 8 are located, and therefore,when the adjustment films 8 are shaved for the frequency adjustment, thewall surface 29 blocks off the scattering shavings to reduce theadhesion of the shavings to the excitation electrodes 6 a, 6 b, 6 c.This prevents the occurrence of a failure of the quartz-crystalresonator due to a short-circuit or the like of the excitationelectrodes 6 a, 6 b, 6 c.

Further, in this embodiment, the wall portion 27 physically prevents theshavings of the adjustment films 8 from adhering to the excitationelectrodes 6 a, 6 b, 6 c. Therefore, even if the excitation electrodes 6a, 6 b, 6 c and the adjustment films 8 are formed up to the vicinity ofthe passage area 28 of the wall portion 27, it is possible to preventthe shavings of the adjustment films 8 from adhering to the excitationelectrodes 6 a, 6 b, 6 c. This allows an increase in an area where theadjustment films 8 can be formed, which makes it possible to thin thethickness of the adjustment films 8 to enable subtler frequencyadjustment. Therefore, a rough adjusting area and a fine adjustment areacan be set, the former being set in such a manner that, for example, theadjustment films 8 with a large thickness are formed in part of theformation area of the adjustment films 8, for example, on one of thefront surfaces 2 a and the rear surfaces 2 b of the oscillating arms 2or are formed in a local area close to the tips of the oscillating arms2, and the latter being set in such a manner that, for example, theadjustment films 8 with a smaller thickness than that in the roughadjustment area are formed in the other area.

Incidentally, in this embodiment, the discharge port 24 is provided inthe bottom portion of the casing 20, but as an embodiment of the presentinvention, if the residual shavings of the adjustment films in thecasing is tolerated because of a reason that, for example, an amount ofthe shaved adjustment films is small or the like, the discharge portneed not be provided. In this case, it is possible to make theatmosphere in the casing vacuum when the quartz-crystal resonatorelement is mounted in the casing and the casing is sealed by the cover,and in this state, the laser cutter is allowed to shave the adjustmentfilms. This makes it possible to eliminate the process of sealing thedischarge port.

OTHER EMBODIMENTS

A quartz-crystal resonator shown in FIGS. 6( a) to 6(c) as anotherembodiment of the present invention has a casing 220, a cover 220 a, anda quartz-crystal resonator element 210, and is structured such that thequartz-crystal resonator element 210 is mounted in the casing 220 andthe cover 220 a is attached to seal the casing 220. The quartz-crystalresonator has the same shape as that of the quartz-crystal resonator ofthe first embodiment except in that the discharge port 24 is not formedin the casing 220, the upper wall portion 26 is not formed in the cover220 a, and adjustment films 208 are different in shape from theadjustment films 8.

In this quartz-crystal resonator, the upper wall portion is not formedin the cover 220 a, and therefore, when the quartz-crystal resonator isassembled, there is only a lower wall portion 225 formed between anatmosphere where excitation electrodes 206 c are located and anatmosphere where the adjustment films 208 are located inside the casing220 as shown in FIGS. 6( b) and 6(c). Therefore, in this quartz-crystalresonator, an upper area in the casing 220 which is closed by the upperwall portion 26 in the first embodiment is open as shown in FIG. 6( c),so that the atmosphere where the excitation electrodes 206 c are locatedand the atmosphere where the adjustment films 208 are located arecontinuously formed.

Therefore, in this quartz-crystal resonator, in order to preventscattering shavings of the adjustment films 208 from entering theatmosphere where the excitation electrodes 206 c are located andadhering to the excitation electrodes 206 c, the excitation electrodes206 c and the adjustment films 208 are provided to be apart from eachother by, for example, a 50.mu.m distance (see FIG. 7( a)) so that theshavings of the adjustment films 208 on front surfaces 202 a, even ifscattering, do not reach the excitation electrodes 206 c. Note that theadjustment films 208 on rear surfaces 202 b and side surfaces ofoscillating arms 202 are formed in the same manner as those of the firstembodiment.

At the time of the frequency adjustment of such a quartz-crystalresonator, when the evaporating adjustment films 8, the shavings, and soon need to be discharged to the outside, the frequency adjustment ismade before the sealing by the cover 220 a, that is, while an uppersurface of the casing 220 is open since the discharge port 24 is notformed in the casing 220. When the adjustment films 208 on the frontsurfaces 202 a are shaved, the shavings of the adjustment films 208enter the atmosphere where the excitation electrodes 206 c are locatedbut the shavings drop to the oscillating arms 202 and a bottom portionof the casing 220 before reaching the excitation electrodes 206 c. Onthe other hand, the shavings of the adjustment films 208 formed on therear surfaces 202 b collide with a wall surface 229 of the lower wallportion 225 as shown in FIG. 7( b) and drop toward the atmosphere wherethe adjustment films 208 are located in a similar manner to that in thefirst embodiment.

Then, the evaporating adjustment films 8 and the shavings are sucked bya vacuum pump from the upper surface of the casing 220 to be dischargedto the outside as shown in FIG. 7( c) since a process of shaving theadjustment films 8 is performed in a vacuum chamber. Thereafter, thecover 220 a is attached as shown in FIGS. 6( b), 6(c). Through the aboveprocesses, the quartz-crystal resonator is manufactured in thisembodiment.

Another frequency adjusting method of this embodiment may be to turn thecasing 220 upside down and shave the adjustment films 208 by a lasercutter 30 from the bottom portion of the casing 220 while the open uppersurface is facing downward, as shown in, for example, in FIG. 7( d).When the casing 220 is thus turned upside down, the shavings of theadjustment films 208 drop by their own weight and are sucked to bedischarged from the open upper surface to the outside of the casing 220,and therefore the shavings of the adjustment films 208 do not accumulateinside the casing 220, which can simplify the discharge process.

In the quartz-crystal resonator of the above-described embodiment, thescattering shavings collide with the wall surface 229 and do not scattertoward the atmosphere where the excitation electrodes 206 a, 206 b, 206c are located when the adjustment films 208 are cut for the frequencyadjustment as in the first embodiment, and therefore, it is possible toadjust the frequency of the quartz-crystal resonator while preventingthe shavings of the adjustment films 208 from adhering to the excitationelectrodes 206 a, 206 b, 206 c. Incidentally, in the embodiment shown inFIG. 7( a), since the irradiation of a laser beam of the laser cutter 30is possible without the laser beam passing through the casing 220, thecasing need not be made of a material capable of transmitting the laserbeam in this embodiment.

Further, a form shown in, for example, FIGS. 8 a) and 8(b) may be anembodiment of the present invention. In this quartz-crystal resonator, alower filling portion 325 is provided in a casing 320 and an upperfilling portion 326 is provided in a cover 320 a. When a quartz-crystalresonator element 310 is mounted in the casing 320, the lower fillingportion 325 and the upper filling portion 326 fill a space of anatmosphere where excitation electrodes 306 a, 306 b, 306 c are locatedso as not to hinder the oscillation of the quartz-crystal resonatorelement 310, so that a volume of an atmosphere where the excitationelectrodes 306 a, 306 b, 306 c are located is reduced as much aspossible. Even when the lower filling portion 325 and the upper fillingportion 326 are thus provided instead of the wall portion, side surfacesof the lower filling portions 325 and the upper filling portion 326become a wall surface 329 corresponding to the wall surface of thepresent invention, so that the wall surface 329 can prevent thescattering shavings from adhering to the excitation electrodes 306 a,306 b, 306 c. Therefore, in such a quartz-crystal resonator, it is alsopossible to adjust the frequency of the quartz-crystal resonator in thesame manner as in the first embodiment.

1. A piezoelectric resonator comprising: a casing; a piezoelectricresonator element housed in the casing and including: a tuning-forkpiezoelectric oscillating piece from whose base portion two oscillatingarms extend in parallel with each other; excitation electrodes formed onthe oscillating arms; adjustment films for frequency adjustment formedon tip sides of the oscillating arms so as to be apart from theexcitation electrodes; and a lead electrode formed on the base portion;and a wall surface provided in the casing, located between an atmospherewhere the excitation electrodes are located and an atmosphere where theadjustment films are located, and preventing shavings from scattering tothe atmosphere where the excitation electrodes are located when theadjustment films are shaved.
 2. The piezoelectric resonator according toclaim 1, wherein the wall surface is a surface facing an adjustment filmside of one of the adjustment films and projects from an inner wallsurface of the casing.
 3. An electronic component comprising: thepiezoelectric resonator according to claim 2; a substrate on which thepiezoelectric resonator is mounted; and an oscillator circuitoscillating the piezoelectric resonator.
 4. The piezoelectric resonatoraccording to 1, wherein a portion of the casing, facing at least onesurface side of the adjustment film formation area of the piezoelectricoscillating piece, is made of a light transmitting material and thecasing has a discharge port for discharging the shavings on a sidefacing the atmosphere where the adjustment films are located.
 5. Anelectronic component comprising: the piezoelectric resonator accordingto claim 4; a substrate on which the piezoelectric resonator is mounted;and an oscillator circuit oscillating the piezoelectric resonator.
 6. Anelectronic component comprising: the piezoelectric resonator accordingto claim 1; a substrate on which the piezoelectric resonator is mounted;and an oscillator circuit oscillating the piezoelectric resonator.